1. Field of the Invention
The present invention relates to a direction detecting device and a direction detecting system for detecting a direction of an object.
2. Description of the Related Art
In a conventional direction detecting device, a transmitting signal is encoded with a code having a high autocorrelation for generating a transmitting wave. The transmitting wave is transmitted by a transmitter means and a reflected wave reflected by an object is received by a receiver means. The received reflected wave is orthogonally demodulated for generating a received signal. Then, a correlation between the transmitting signal and the received signal is calculated, that is, a pulse compression is performed. Thereby, a signal-to-noise ration (S/N ratio) is improved and a distance from the direction detecting device to the object is detected by using absolute value information of a result of the correlation calculation, as described, for example, in US 2005/0135190 A (corresponding to JP-A-2005-249770).
A conventional method of detecting a direction of an object by using absolute value information of a received signal includes a triangulation method. In the triangulation method, a reflected wave reflected by the object is received by a plurality of receiver elements, and a difference in receiving times of the received signals of the receiver elements is used for detecting the distance of the object. Thus, in the triangulation method, the direction detecting device is required to detect the difference in the receiving times with a high degree of accuracy. The difference in the receiving times depends on a distance between the receiver elements. When the distance between the receiver elements decreases, the difference in the receiving times also decreases. Thus, the direction detecting device is difficult to detect the direction of the object with a high degree of accuracy.